In lighting applications it is desirable to produce light sources showing sparkling effects. Such effects are usually produced using refractive optical components placed in front of a LED light source. An example is described in WO 2010/131129 A1.
In this way, high intensity light sources can produce such sparkling effects for applications such as e.g. LED candle lamps. For many applications, it is also important to produce such effects for aesthetics. However, multiple refractive components for light sources are rather expensive, and the larger the size of the refractive component required, the more expensive it is.
Furthermore, in some applications, such as retrofit capsules, it has been shown that the lumen output can be increased considerably by using a phosphor arranged in a distance from the light source. In such an arrangement, however, any sparkling effect otherwise provided for disappears.
Furthermore, US 2012/0218752 A1 describes a lighting module for a backlight unit such as a liquid crystal display. This lighting module comprises a light source, a diffuser arranged in front of the light source and a reflective sheet arranged between the light source and the diffuser and provided with holes, the reflective sheet being arranged at a distance from both light source and diffuser. The reflective sheet serves the purpose of blocking part of the light emitted by the light source, such that the amount of light transmitted through the reflective sheet corresponds to the amount of light transmitted through the holes therein. The aim of this lighting module is to obtain a uniform illumination light with reduced variations in brightness. Therefore this solution does not provide any sparkling effect.
Hence, the prior art solutions provide either a sparkling effect, these solutions being rather expensive, or a high lumen light output. Such lighting devices consequently provide a light output, which is perceived as unsatisfactory by a viewer in terms of light intensity, aesthetical appearance or both.